I recently had to add a CSS class to all validators in an ASP.NET web application. I started with the theme’s skin file:

<asp:CompareValidatorrunat="server" CssClass="error"/>
<asp:CustomValidatorrunat="server" CssClass="error"/>
<asp:RequiredFieldValidatorrunat="server" CssClass="error"/>
<belCommon:ZipCodeValidatorrunat="server" CssClass="error"/>
<belCommon:PhoneNumberValidatorrunat="server" CssClass="error"/>

But what if I decide to use another validator down the road? I would have to remember to add it to the skin. Knowing that I was bound to forget, I sought out another method. After doing some digging, I found that ASP.NET generates a JavaScript variable called Page_Validators. This is an array of all the validator span elements on the current page. Now that I have access to the spans, I could write a script in the site’s Master Page to apply the class:

if (Page_Validators != null) 
{ 
    for (i = 0; i < Page_Validators.length; i++) 
    { 
        Page_Validators[i].className = "error"; 
     }
}

To have it run when the page is loaded, I added it as an Sys.Application.init handler:

Sys.Application.add_init(function(sender, args) { 
    if (Page_Validators != null) { 
        for (i = 0; i < Page_Validators.length; i++) { 
            Page_Validators[i].className = "error"; 
        } 
    } 
});

You could also use jQuery’s document.ready handler:

$(document).ready(function() { 
    if (Page_Validators != null) { 
        for (i = 0; i < Page_Validators.length; i++) { 
            Page_Validators[i].className = "error"; 
        } 
    } 
});